The present invention relates generally to the field of electrical neuromuscular stimulation for controlling urinary incontinence in women. In particular, the present invention is a molded vaginal electrode having increased effectiveness and a simplified method of construction.
Electrical neuromuscular stimulation is widely used to assist persons afflicted with motor dysfunctions in performing muscle contraction maneuvers. Motor nerve fibers are electrically stimulated by means of transcutaneously applied pulses of electrical current to cause contraction of the innervated muscles. This technique is also used to re-educate patients in the proper use of the dysfunctional muscles.
For example, in cases in which urinary incontinence in women is caused by the patient's inability to properly contract the external sphincter of the urethra, it has been shown that neuromuscular stimulation of the dysfunctional muscles by means of a vaginal or anal electrode can effectively prevent the unwanted flow of urine. Furthermore, through the use of such an electrode some patients can educate themselves to voluntarily or automatically impede the flow of urine.
Electrical stimulators for controlling urinary incontinence generally include a vaginal plug with one or more electrodes in the form of conductive metal rings. The metal bands tend to cause intravaginal current density burns by the "edge effect". The "edge effect" is the tendency for the current density to be maximum at the edges of a conductor having a surface impedance considerably lower than the adjacent tissue. When the plug is inserted, the electrodes contact the vaginal wall. Conductive carbon-loaded silicone rubber substantially decreases "edge effect" to safe values, as its surface impedance can be made close to vaginal tissue impedance. Also, conductive silicone is lighter in weight than the metal electrode, which avoids the problem of the weight of the electrode causing it to fall out of the vagina. A lead harness extends from the plug to a controller or stimulator which generates stimulation signals. The controller is typically worn externally, attached to the user's clothing.
The vaginal electrode of the present invention provides an improved means for coupling electrical energy to a conductive polymer electrode. Other coupling methods such as molding the conductive polymer directly to the metal contact or using adhesives to bond the metal contact to the conductive polymer have proven ineffective. Various factors, such as heat-induced pull-away of the polymeric compounds from the metal contacts in the molding process, "stress creep" (elastomeric relaxation) of the polymeric compounds, flexing of the vaginal electrode due to contractions of the vaginal muscles, and swelling of the vaginal electrode due to absorption of vaginal fluids, have resulted in diminished contact integrity between the metal and the conductive polymer thereby increasing the electrical impedance and decreasing the effectiveness of the electrode.
There is a continuing need for improved vaginal electrodes which can be used to prevent the unwanted flow of urine. In addition to being effective, the electrode must be durable, hygienical and inexpensive to manufacture.